void MurmurHash3_x86_32()

in src/iceberg/util/murmurhash3_internal.cc [87:141]

• 34 lines of code
• 5 McCabe index (conditional complexity)

void MurmurHash3_x86_32(const void* key, int len, uint32_t seed, void* out) {
  const uint8_t* data = (const uint8_t*)key;
  const int nblocks = len / 4;

  uint32_t h1 = seed;

  const uint32_t c1 = 0xcc9e2d51;
  const uint32_t c2 = 0x1b873593;

  //----------
  // body

  const uint32_t* blocks = (const uint32_t*)(data + nblocks * 4);

  for (int i = -nblocks; i; i++) {
    uint32_t k1 = getblock32(blocks, i);

    k1 *= c1;
    k1 = ROTL32(k1, 15);
    k1 *= c2;

    h1 ^= k1;
    h1 = ROTL32(h1, 13);
    h1 = h1 * 5 + 0xe6546b64;
  }

  //----------
  // tail

  const uint8_t* tail = (const uint8_t*)(data + nblocks * 4);

  uint32_t k1 = 0;

  switch (len & 3) {
    case 3:
      k1 ^= tail[2] << 16;
    case 2:
      k1 ^= tail[1] << 8;
    case 1:
      k1 ^= tail[0];
      k1 *= c1;
      k1 = ROTL32(k1, 15);
      k1 *= c2;
      h1 ^= k1;
  };

  //----------
  // finalization

  h1 ^= len;

  h1 = fmix32(h1);

  *(uint32_t*)out = h1;
}